We're in a weird moment in the campaign. Trump is the presumptive Republican nominee. Clinton, technically, is not yet the Democratic nominee. This is a disadvantage for Clinton, but one that will persist only for a few more weeks.

Depending on the poll, something like 30% of Bernie Sanders supporters are still saying they won't vote for Clinton if she is nominated. Some fraction of Sanders supporters really will withhold their support from Clinton, but it likely won't be as large as the polls show now.

Remember: This isn't the first campaign where the backers of a losing candidate for the nomination have claimed they wouldn't unify behind the nominee:

It's possible Clinton will have a bigger party-unity problem than Barack Obama did eight years ago. Certainly, the policy differences between Sanders and Clinton are larger than those between Clinton and Obama eight years ago.

But the ideological gap between Sanders and Clinton voters is not necessarily as large as the ideological gap between Sanders and Clinton themselves. Plus, the possibility of a President Donald Trump is likely to be a unifying force on the left.

Basically, we don't know yet how recalcitrant Sanders' supporters really will be. And we can't know until he gets out of the race and pollsters get to talk with Sanders fans outside the heat of what many of them, for whatever reason, still believe is a live fight for the nomination.

I'm laying down the marker now: If the polls still show this race close to tied on July 1, after all the Democratic primary voting is over and Sanders has ended his campaign, I'll believe it's close to tied.

Until then, my view remains what it was a month ago: Donald Trump is too unpopular to win a general election, and Hillary Clinton is an overwhelming favorite to beat him.